Definition of "trophoblast" [trophoblast]

• The outermost layer of cells of the blastocyst that attaches the fertilized ovum to the uterine wall and serves as a nutritive pathway for the embryo. Also called trophoderm. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "A typical day-5 human embryo consists of 200-250 cells, most of which comprise the trophoblast, which is the outermost layer of the blastocyst."
• "In a healthy pregnancy, cells that come from the embryo's placenta-called trophoblast cells-move into the walls of the uterus and help to open up maternal arteries, thereby increasing the available blood and nutrient supply."
• "Perhaps they're hoping the the terms "trophoblast", "blastocoel", and "blastocyst" will disguise the fact that we're talking about a human being?"